Flavonoids are a large class of compounds widely distributed in nature.  Many pharmacological activities of flavonoids have been reported such as anti-cancer, antioxidant, anti-inflammatory, hepatoprotective, antithrombotic, vasodilator, antiviral, antibacterial, antiallergic, and so on.  In recent years, domestic and foreign research groups choose natural flavonoids and optimize their chemical structures in order to develop a number of new derivatives with stronger pharmacological activities.  As part of the mechanisms are not clear, we need to strengthen in-depth research in the SAR (structure-activity relationship) study for targeted and efficient structure optimization.  This paper systematically summarize current researches in the SAR studies of flavonoids and their derivatives, which can serve as a reference for synthesizing new flavonoid derivatives.